This is what they write on the website you linked to:

1,487,733 of the 9,542,183 million non-voting and seldom-voting environmentalists whom EVP has communicated with since the fall of 2015 are now consistent super-voters who vote in every election, big and small.

All in all there are about 139,398,590 environmentalists in the USA (41% of Americans identify themselves as "environmentalists").

How do you know that climate protestors aren't in the big group of environmentalists who vote?